Malic acid, HOCOHCH.sub.2 CH(OH)COOH, a white triclinic crystalline powder, is well known to be a general-purpose acidulant. It is produced synthetically by catalytic oxidation of benzene to maleic acid, which is converted to malic acid by heating with steam under pressure. The commercial synthetic product is a racemic mixture of the D- and L-isomers. Unless stated otherwise, the term "malic acid" as used in the specification and claims refers to both the DL (racemic) and L forms. Malic acid is approved by the FDA as a GRAS (Generally Recognized As Safe) compound for miscellaneous and/or general-purpose food additive use.
DeVuyst et al. in Revue de d'agriculture, Volume 1, pp. 35-41, January-February 1974, describe a feeding experiment in which 2% (of feed weight) malic acid was added to the weaning feed of milk-fed veal calves. The study concluded that the malic acid did not in any way improve the performance of veal calves under the given experimental conditions. In fact, the growth rate of the calves fed malic acid was 7.5% less than the growth rate of the control group.
J. T. Barr, in a graduate thesis entitled "The Influence of Addition of Certain Organic Acids on Nitrogen Metabolism and Energy Digestibility in Holstein Bulls" (University of Arkansas, Fayetteville, 1969, Library Identification SF/203/B34) describes experiments in which bulls were fed basal diets supplemented by 108.0 g urea and 70.0 g malic acid. The basal diet consisted of 4 kg prairie hay and 1 kg of 87% cane molasses on soybean hulls. It was discovered that there was greater mean nitrogen retention and mean digestibility of crude portein when the bulls were fed a malic acid-supplemented diet than when the bulls were fed identical diets absent the malic acid.